As an undergraduate, Atkinson read Simone de Beauvoir's The Second Sex, and struck up a correspondence with Beauvoir, who suggested that she contact Betty Friedan.[6] Atkinson thus became an early member of the National Organization for Women, which Friedan had founded, serving on the national board, and becoming the New York chapter president in 1967.[7] In 1968 she left the organization because it would not confront issues like abortion and marriage inequalties.[4] She founded the October 17th Movement, which later morphed into The Feminists, a radical feminist group active until 1973. By 1971 she had written several pamphlets on feminism, was a member of the Daughters of Bilitis and was advocating specifically political lesbianism.[8] Her best known book, Amazon Odyssey, was published in 1974.[9]

After she left The Feminists she said, “Sisterhood is powerful. It kills. Mostly sisters," which was often quoted by feminists, although often without the word "mostly."[10]

In 2013 Atkinson, along with Carol Hanisch, Kathy Scarbrough and Kathie Sarachild, initiated "Forbidden Discourse: The Silencing of Feminist Criticism of 'Gender'", which they described as an "open statement from 48 radical feminists from seven countries".[11] In August 2014 Michelle Goldberg in the The New Yorker described it as expressing their “alarm” at “threats and attacks, some of them physical, on individuals and organizations daring to challenge the currently fashionable concept of gender.”[12]